Increasing the tenacity of cellulose acetate yarns



Patented Apr. 25, 1953 INCREASING THE TENACITY OF CELLULOSE ACETATEYARNS Thomas Jackson and Frank Brentnall Hill, Spondon, near Derby,England, assignors to Celanese Corporation of America, a corporation ofDelaware No Drawing. Application March 6, 1946, Serial No. 652,484. InGreat Britain March 14, 1945 2 Claims.

This invention relates to improvements in the treatment of materialsmade of organic derivatives of cellulose, and particularly toimprovements in the stretching of filaments having a basis of an organicderivative of cellulose.

The stretching of filaments and other materials made of celluloseacetate or other organic derivative of cellulose in wet steam or hotwater has been described in a number of prior specifications. Forexample, U. S. Patent No. 2,142,909 describes a process in whichfilaments, threads and similar materials of an organic derivative ofcellulose are stretched during their passage through an apparatuscomprising an end' pressure chamber containing compressed air or otherinert gas and a stretching chamber containing saturated or wet steam ata temperature above 100 C. In this manner the tenacity of the materialsmay be increased.

The above process gives excellent results starting from the ordinarycommercial filaments of cellulose acetate, namely filaments of the orderof 2 to 5 denier. Indeed such results are obtainable with filamentdeniers considerably higher than the commercial deniers, such as to 15.When filaments having a denier of 2 to 10 or are stretched 10 or times,the resulting filaments have a denier of 0.1 to 1.5. When thesefilaments are completely saponified to regenerated cellulose, thefilament deniers then become of the order of 0.06 to 1 denier. For somepurposes strong yarns are required composed of filaments having higherdeniers than the extremely fine ones mentioned, for example regeneratedcellulose filaments having deniers of the order of 5 to 10.

This necessitates starting with filament deniers of '75 to 150. It isfrequently found when starting with filaments of such very high denieras '75 to 150, or even lower denier, for instance or 30, that theimprovement in the tenacity obtained by stretching is not so great asthat obtained when stretching filaments of the ordinary commercialdeniers, such as 2 to 5 or 10. This is more particularly the case whenthe speed at which the filaments are drawn away from the point ofstretching is high, for example, 150 to 200 metres per minute at whichspeed the stretching of lower denier filaments, for example filaments of5 to 10 denier, can readily be effected to obtain products of goodproperties.

It has now been found that it is very advantageous if, prior tostretching, filaments made of organic derivatives of cellulose aresoaked in water until they are thoroughly wet-out. Most convenientlythey are soaked in package form, e. g.

in hanks or on bobbins, for a considerable time, for instance for 1, 5,10 or 20 hours or more. This preliminary soaking enables the filamentsto be stretched at higher speeds than can be employed in the absence ofthe soaking without sacrificing the properties of the products in somemeasure.

By the term thoroughly wet out as applied to the filaments is meant thatthe filaments are 'permeated. with water and that their water content isa substantial proportion of that which the filaments contain when inequilibrium with water. Preferably the water content is substantiallythat which the filaments contain when in equilibrium with water.Wetting-out may be assisted by the use of a wetting agent, e. g. analkyl naphthalene sulphonic acid, a sulphonic acid ester of lauryl,oleyl or other higher aliphatic alcohol or Turkey red oil. Soaking maybe carried out at atmospheric temperature or the water may be heated,for example to a temperature of 50 or C.

The value of the soaking is most marked when the stretching is carriedout in wet steam, though it is also advantageous if hot water isemployed as the stretch-assisting agent.

The stretching conditions which are suitable are similar to thosedescribed in U. S. Patent No. 2,142,909. The degree of stretch employedis usually about ten to twenty times, using wet steam or hot Water at atemperature between to 145 C. according to the nature of the cellulosederivative, e. g. its viscosity and the kind and proportion ofsubstituent radicles. The higher the viscosity of a cellulose derivativethe higher in general is the temperature of the hot water or wet steamwhich gives the best results, provided that the cellulose derivativesare otherwise comparable, e. g. as regards the degree of substitutionand the nature of the substituent radicle. For example, filaments madeof an acetone-soluble cellulose acetate of 10 to 20 viscosity give goodresults when stretched in wet steam at a temperature of 133 to 135 C.,whereas if made of one of 80 to 100 viscosity the temperature of the Wetsteam should be increased to about 143 to 145 C. The viscosities givenabove are obtained by comparing the rate of flow of a 6% solution of theacetate in acetone at 25 C. with the rate of fiow of glycerin under thesame conditions. For this purpose the viscosity of glycerin is taken as100.

Filaments which are to be stretched in accordance with the presentinvention may be produced by extruding a solution or plastic mass havinga basis of cellulose acetate, cellulose propionate, cellulose butyrate,cellulose acetate-butyrate or other organic derivative of cellulosethrough an orifice of such dimensions that filaments of high denier aredirectly produced, or they may be obtained by coalescing a number offilaments of lower denier, for example as described in British PatentNo. 326,462. Thus an acetone solution of cellulose acetatemayjbe .spunin,an ordinary dry.- spinning cell to give a bundle of filaments, eachof which has a denier of about 6, and this bundle of filaments onissuing from the cell may be passed over a wick which is impregnatedwith acetone and from there round areedrone l and) over a lubricatingwick to a bobbin up device.

This method gives a coalesced, monofilament having a denier, forexample'fof 120 120-150, according to the number and denier of thefilaor other take ments in the bundle, which cambe. stretched by. theprocess of the present invention togive a product having a tenacity of 4to 5 grams. .per. For instance, three ends of coalesced denier. yarn,each of which has adenier of 150, may be stretched' 't'o tentimes theiroriginal length in wet steam at a temperature of 1'30 to 145' Cl and mayThe following examplefis given to illustrate the invention:

" Example.

A, mQ o ilament .Of 150 denier, made as..de

scribed Y in British Patent No, 326,462 by coalescing a number of"filaments. of. lower, denier havingjabasis of acetone-soluble celluloseacetate was soaked, in package form? in .water. for. six,

to give a stretched,

aqueous solution of o;M. P. g, while it "is passedthroilgh w t steamsuch as that illustratedifri S..,'PatentNo.12,1' l2,- 909': using [waterin the.l end ..cha'mber. The.

al mel D9 'denierfwhereas when .1 stretching was: carried out without smerit iniwater the tenacityf the stretched 'fila-.

merit was only about 3' gramme per denier. tionfha's been. w sgmegpr- Te proces o thep es it in described abova'ini .relatio presence ofwet-Steam at filaments of high denier having a basis of acetone-solubleacetate, since it is for this purpose that it is of greatest importance.It is, however, also applicable to the stretching of filaments made ofother organic derivatives of cellulose, e. g. cellulose' propionate,OGHUlQSB f butyrate,v cellulose acetate-'butyrate and ethyl cellulose.

Having described our invention, what we desire to secure by LettersPatent is:

a, ;process, for. producing high-tenacity yarns having a basis of anacetone-soluble cellulose acetateanda denier of at least 5 bystretchyarn'slhavinga' filament-denier of at least ,atileast ten timestheir original length in the a temperature above 0., the improvementwhich consists in immersing theyarninpackage form for at least 16 hoursin water at a' temperature below 50 C., andsubiecting it to thestretching treatment as the next operation.

1;, a. process. for pmduc n msh t amty yarns havingla..basis of an acetone-solublev cellulose acetate and a denienof atleastifi bystretch:

ing 'yaitnsjhavinga filamentedenierof at least 75 ,by at leastten timestheir original length in the,

presence of. wetv steam. at. a, temperature above 130. C'., theoutputspeed of. theyarn from the being, .at..leaSi'-; 15Q meters.

per minute, the. improvement which. consists in ,immeltsing. the. yarninpackage form for atleast.

stretching apparatus 16 hours in .water. .atia ..temperatu;rebelow/500.,

e. sifllemiat on:

T QMASJAC QN-v REEERENQES' CITED.

The. following: references are, of recordin the;

file of this patent:

UNITED-STATES PATENTS Number Name v Date 2,951,331 Dreyfus Aug. 25,1936, 070,58 16, 1937 RE Q PATENTS-c Number Country Date 22 1; reatB an---.----.-- ul '1; 1 3 1 12 G aFiBrit in--- .-.--.APr-.2 32

1. IN A PROCESS FOR PRODUCING HIGH-TENACITY YARNS HAVING A BASIS OF ANACETONE-SOLUBLE CELLULOSE ACETATE AND A DENIER OF AT LEAST 5 BYSTRETCHING YARNS HAVING A FILAMENT-DENIER OF AT LEAST 75 BY AT LEAST TENTIMES THEIR ORIGINAL LENGTH IN THE PRESENCE OF WET STEAM AT ATEMPERATURE ABOVE 130*C., THE IMPROVEMENT WHICH CONSISTS IN IMMERSINGTHE YARN IN PACKAGE FORM FOR AT LEAST 16 HOURS IN WATER AT A TEMPERATUREBELOW 50*C., AND SUBJECTING IT TO THE STRETCHING TREATMENT AS THE NEXTOPERATION.